Scion of a prominent Bolognese family of jurists, T., who was the third son of Joannes Zaccarius, q.v., first studied philosophy at Padova, but then went to Bologna where he earned a doctorate in utroque in 1512 with further studies in canon law, which he completed in 1514. He then became an official and diplomat for the Holy See, frequently in the company of his brother Lorenzo, who was a cardinal. He was the nuncio at the Protestant-Catholic talks at Worms in 1540 and attended at least some of the sessions of the council of Trent.

Over the course of long career as a papal official, T. managed to write a great deal. TUI 1584 reprints thirteen of his treatises, most of them quite short. His De potestate conciliorum (TUI 1584, 13.1) is exceptional both for its length and for its quality. Although it does not ignore the law, it approaches the issue more from an historical point of view and thus makes the reader aware of the changes over time in the relationship between pope and council. It also gives us detail about the procedures used at the council of Trent. That the man who wrote this treatise was also one of those who were open to listening to the arguments of the reformers at the council is not surprising.